A member of Saudi Crown Prince Mohammed bin Salman's entourage walked into the Saudi consulate in Istanbul just before writer Jamal Khashoggi vanished there, according to a leaked surveillance photo.

The man, identified by Turkish officials as Maher Abdulaziz Mutreb, has been photographed in the background during the prince's trips to the US, France, and Spain this year.

Turkish officials say he flew into Istanbul on a private jet along with an "autopsy expert" on October 2 and left that night.

That was the same day Khashoggi, a columnist for The Washington Post who wrote critically of the prince's rise to power, entered the consulate and was never seen again.

Turkish press reports - which commentators suspect are based on deliberate government leaks - have suggested that Khashoggi was killed by a 15-person "assassination team" who flew in on two chartered planes to interrogate, torture and kill him.

Saudi Arabia has called the allegations "baseless".

'Head of execution squad'

On Thursday, the pro-Turkish government Sabah newspaper first published the images of Mutreb, showing him walking past police barricades at the consulate at 9:55am with several men trailing behind him.

Khashoggi arrived at the consulate several hours later at 1:14pm, then disappeared while his fiancee waited outside for him.

A Wednesday report by pro-government newspaper Yeni Safak, citing what it described as an audio recording of Khashoggi's killing, said a Saudi team immediately accosted the 60-year-old journalist after he entered the consulate, cutting off his fingers and later decapitating him.

Previously leaked surveillance footage showed consular vehicles moving from the consulate to the consul general's official residence, a few hundred metres away, a little under two hours after Khashoggi walked inside.

Thepictures published by Sabah showed an image of Mutreb at 4:53pm at the consul's home, then at 5:15pm checking out of a hotel. He later cleared an airport security check at 5:58pm before flying out of Istanbul.

The report identified him as the alleged head of the 15-man "execution squad".

The Associated Press said Saudi Arabia had not responded to repeated requests for comment over recent days, including on Thursday over Mutreb's identification.

Mutreb could not be reached for comment immediately, the news agency said.

Ties to Prince Mohammed

The New York Times has meanwhile reported that at least nine of the 15 suspects worked for the Saudi security services, military or other government ministries.

Four of them, including Mutreb, are linked to bin Salman's security detail, while a fifth man is a high-level forensic doctor, the Times said.

The Times identified the suspects with links to bin Salman as Abdulaziz Mohammed al-Hawsawi - a member of the security team that travels with the prince - Thaar Ghaleb al-Harbi and Muhammed Saad Alzahrani.

Al-Harbi and Alzahrani have the same names as two people who have been identified as members of the Saudi Royal Guard, the Times said.

The forensic expert was named as Salah al-Tubaigy, who the Times said identified himself on his Twitter account as the head of the Saudi Scientific Council of Forensics.

He also held high positions in the Interior Ministry and the kingdom's top medical school, the report said.

In a separate report late on Tuesday, the Washington Post said 11 of the 15 people who Turkey alleged were involved in Khashoggi's killing have ties to the Saudi security services, including some who claim to be with the Royal Guard.